1. Field of the Invention
The present invention relates to a magnetic heater for use as auxiliary heating means of heat transferring fluid such as engine cooling water used for improving the starting performance of various vehicular engines of cars in particular whose power source is a diesel engine or a gasoline engine and for heating a cabin of various vehicles including electric cars and ships when the weather is cold or is extremely cold and for use in a generator driven by an engine, a welding machine, a compressor, a unit for preheating or quickly heating engine cooling water of construction machines (to shorten warming up time), a unit for forced-feeding hot water while heating, a heater of an air conditioner and a dryer such as a hair dryer.
2. Description of the Related Art
There has been known a viscous type heater as a vehicular auxiliary heating source of a car and the like used for heating engine cooling water in starting the car in a cold district (see JP-A-2-246823, JP-A-4-11716U, JP-A-9-254637, JP-A-966729, JP-A-9-323530 and others).
The viscous type heater is a system which causes viscous fluid such as silicon oil to generate heat by shearing and utilizes the heat as a heating source by heat-exchanging it with circulating water circulating within a water jacket. It comprises an exothermic chamber within a housing, the water jacket formed on the outside of the exothermic chamber, a driving shaft rotably supported by the housing via a bearing and a rotor which is turnable within the exothermic chamber and which is fixed to the driving shaft. The viscous fluid such as the silicon oil is filled in a gap between the wall face of the exothermic chamber and the rotor. The circulating water circulates within the water jacket so that it is taken in from a water inlet port and is sent out to an external heating circuit from a water outlet port.
When the driving shaft is driven by an engine, the rotor rotates within the exothermic chamber in the viscous type heater incorporated in a heating system of a vehicle. Then, the viscous fluid generates heat by being sheared at the gap between the wall face of the exothermic chamber and the outer face of the rotor. This heat is heat-exchanged with the circulating water within the water jacket and the heated circulating water is utilized to heat the vehicle such as the engine cooling water.
However, although the viscous type heater described above has had advantages that its simple structure allows the miniaturization and the low cost to be realized, its non-wearing and non-contact mechanism allows high reliability and safety to be maintained and it uses no wasteful energy because its operation stops automatically by temperature control when the water temperature rises and the auxiliary heater is not required, it has had problems that the temperature of the silicon oil used as the viscous fluid cannot be so high because the heat resistance of the silicon oil is around 240.degree. C., it takes time until when the silicon oil generates high temperature heat after being agitated at the start and the heating effect cannot be obtained quickly when the engine is cold because its heating value per unit time tends to decrease gradually because the viscosity drops and the shearing resistance drops when the temperature of the silicon oil increases. Therefore, such viscous type heater has not been fully effective in case of a vehicle specific for a cold district and carrying a diesel engine in particular and an auxiliary heater capable of heating the heat transferring fluid efficiently in a shorter time has been requested.
The present invention has been devised in view of such problems of the viscous type heater and its object is to provide a magnetic heater which is capable of heating the heat transferring fluid to high temperature in a short time and is excels in the heat resistance as compared to the viscous type heater.